Process for saparating a hydroxybenzonitrile-type compound

Abstract

The invention concerns a method for separating a hydroxybenzonitrile-type compound obtained by an amination/dehydration process. More particularly, the invention concerns 2-hydroxybenzonitrile, also called 2-cyanophenol. The inventive method for separating a hydroxybenzonitrile compound from a reaction gas flow comprising it wholly or partly in the form of an ammonium salt is characterized in that it consists in displacing the ammonium ions, through a physical treatment carried out on the reaction gas flow derived from its preparation or from the solid previously recuperated from said flow or according to a chemical treatment carried out on the reaction gas flow, after liquefaction.

1 . A process for separating a hydroxybenzonitrile type compound from a gaseous reaction stream containing it either completely or partially in the form of an ammonium salt, characterized in that it consists, with the aim of obtaining a hydroxybenzonitrile type compound, of displacing the ammonium ions: 
 by means of a physical treatment carried out on the gaseous reaction stream deriving from its preparation or by means of a physical treatment of the solid already recovered from the gaseous reaction stream after liquefaction, or of said same solid in solution;    or by means of a chemical treatment carried out on the gaseous reaction stream after liquefaction.    
   
   
       2 . A process according to  claim 1 , characterized in that the hydroxybenzonitrile type compound has the following formula:  
     
       
         
         
             
             
         
       
       in which formula R represents one or more substituents.  
     
   
   
       3 . A process according to  claim 2 , characterized in that the hydroxybenzonitrile type compound has formula (I) in which R is selected from: 
 linear or branched alkyl groups preferably containing 1 to 6 carbon atoms, more preferably 1 to 4 carbon atoms;    linear or branched alkenyl groups, preferably containing 2 to 6 carbon atoms, more preferably 2 to 4 carbon atoms;    linear or branched halogenoalkyl groups, preferably containing 1 to 6 carbon atoms and 1 to 13 halogen atoms, more preferably 1 to 4 carbon atoms and 1 to 9 halogen atoms;    the hydroxyl group;    the NO 2  group;    R 1 —O— alkoxy or R 1 —S— thioether groups in which R 1  represents a linear or branched alkyl group containing 1 to 6 carbon atoms, more preferably 1 to 4 carbon atoms or the phenyl group; or alkenyloxy groups, preferably an allyloxy group;    R 1 —CO—O— acyloxy or aroyloxy groups in which the group R 1  has the meaning given above;    R 1 —CO— acyl or aroyl groups, in which group R 1  has the meaning given above;    a halogen atom, preferably a fluorine atom;    a CF 3  group.    
   
   
       4 . A process according to  claim 1 , characterized in that the hydroxybenzonitrile type compound is 4-hydroxybenzonitrile or 2-hydroxybenzonitrile.  
   
   
       5 . A process according to  claim 1 , characterized in that the hydroxybenzonitrile type compound is wholly or partially in its hydrated form.  
   
   
       6 . A process according to one  claims 1  to  5 , characterized in that the gaseous reaction stream (F 1 ) essentially comprises 2-hydroxybenzonitrile, either completely or partially in its salt form; preferably, the quantity of 2-hydroxybenzonitrile, expressed as a mole % with respect to the alkyl 2-hydroxybenzoate employed, is at least 50%, preferably at least 75% and still more preferably in the range 80% to 95%.  
   
   
       7 . A process according to  claim 6 , characterized in that gas stream (F 1 ) also comprises ammonium in an amount of 200 to 600 mole %, nitrogen in an amount of 5 to 200 mole %, the alcohol liberated by the starting ester, preferably methanol in an amount of 50 to 100 mole %, water formed during the reaction, about 50 to 100%; optionally 0 to 5 mole % of phenolic compounds, preferably phenol, 0 to 5 mole % of the starting hydroxybenzoate ester, and products resulting from secondary reactions, such as hydrolysis or trimerization, in particular 0 to 10 mole % of 2-hydroxybenzamide optionally N-alkylated by the liberated alcohol, for example N-methyl-(2-hydroxybenzamide), and less than 3 mole % of S-triazine.  
   
   
       8 . A process according to one of  claims 1  to  4 , characterized in that the reaction stream is derived from a process for amination/dehydration of an alkyl hydroxybenzoate consisting of reacting it with ammonia in the gas phase in the presence of a heterogeneous catalyst, preferably phosphoric acid deposited on a silica gel or kieselguhr type support.  
   
   
       9 . A process according to one of  claims 1  to  8 , characterized in that the gaseous reaction stream is at a temperature of 200° C. to 600° C., preferably in the range 350° C. to 450° C.  
   
   
       10 . A process according to  claim 1 , characterized in that it consists of heat treating the gas stream comprising 2-hydroxybenzonitrile completely or partially in its salt form.  
   
   
       11 . A process according to  claim 10 , characterized in that the gaseous reaction stream is brought into contact with a solvent (organic solvent and/or water) then the ensemble is cooled to a temperature of less than 200° C., preferably in the range 200° C. to 100° C., to obtain a liquid phase essentially comprising 2-hydroxybenzonitrile.  
   
   
       12 . A process according to  claim 10  or  claim 11 , characterized in that the solvent (S 1 ) is a polar or apolar solvent, preferably selected from: water, water/alcohol mixtures, preferably methanol or ethanol; halogenated or non halogenated aromatic hydrocarbons, preferably toluene, xylenes, ethylbenzene or monochlorobenzene; and ethers, preferably anisole or 2-ethylhexanol.  
   
   
       13 . A process according to one of  claims 10  to  12 , characterized in that the hot gas stream is brought into contact with the vaporized reaction solvent generally as a co-current and in that light gases (F 2 ) comprising ammonia, alcohol (usually methanol), water and in some cases an azeotropic water/organic solvent mixture are recovered, along with heavy compounds (F 3 ), essentially 2-hydroxybenzonitrile and the solvent (organic solvent and/or water).  
   
   
       14 . A process according to one of  claims 10  to  13 , characterized in that the heavy fraction (F 3 ) essentially comprising 2-hydroxybenzonitrile and solvent is purified by distillation.  
   
   
       15 . A process according to one of  claims 10  to  13 , characterized in that the heavy fraction (F 3 ) essentially comprising 2-hydroxybenzonitrile is purified by crystallization.  
   
   
       16 . A process according to  claim 15 , characterized in that the heavy fraction (F 3 ) is cooled to a temperature in the range 100° C. to −10° C., preferably in the range 10° C. to 0° C., which causes the 2-hydroxybenzonitrile to crystallize; the crystalline product is then separated using conventional solid/liquid separation techniques, preferably by filtration; a solid is recovered that is essentially 2-hydroxybenzonitrile and a liquid phase (F 6 ); and the solid is dried at a temperature in the range 30° C. to 80° C., preferably in the range 40° C. to 50° C.  
   
   
       17 . A process according to one of  claims 10  to  13 , characterized in that the heavy fraction (F 3 ) essentially comprising 2-hydroxybenzonitrile is purified by refining.  
   
   
       18 . A process according to  claim 17 , characterized in that the heavy fraction  3 ) is cooled to a temperature in the range 100° C. to 30° C.; an aqueous phase (F 7 ) and an organic phase (F 7 ) 3 ) which is essentially 2-hydroxybenzonitrile and solvent (S 1 ) are separated; the organic phase is treated to separate the water and/or the solvent by distillation under reduced pressure; and a crude reaction mass essentially comprising 2-hydroxybenzonitrile is recovered which undergoes a purification operation by refining.  
   
   
       19 . A process according to  claim 18 , characterized in that the reaction mass is cooled to a temperature in the range 10° C. to 50° C.; the temperature is raised to between 94° C. and 98° C. to separate eutectic fractions comprising impurities; and it is heated to a temperature of more than 98° C. to melt the 2-hydroxybenzonitrile, which is extracted in the molten state (F 11 ).  
   
   
       20 . A process according to  claim 1 , characterized in that it consists of liquefying the gaseous reaction stream then crystallizing the ammonium cyanophenate, then carrying out a solid/liquid separation and heat treating the solid product obtained.  
   
   
       21 . A process according to  claim 20 , characterized in that firstly, the gaseous reaction stream (F 1 ) is liquefied by cooling from 90° C.-100° C. to a temperature of 40° C.-30° C. and contact with water to eliminate light compounds and to recover an aqueous phase comprising ammonium cyanophenate and ammonia.  
   
   
       22 . A process according to  claim 20 , characterized in that the liquefied stream (F 12 ) is cooled to a temperature in the range 0° C.-30° C. to cause crystallization of the ammonium cyanophenate and the crystallized product is separated using conventional solid/liquid separation techniques, preferably by filtering to recover a solid which is essentially ammonium cyanophenate.  
   
   
       23 . A process according to one of  claims 20  to  22 , characterized in that the heat treatment is then carried out at a temperature in the range 80° C. to 20° C., at a pressure in the range 1 mbar to 1 bar, preferably in the range 1 mbar to 500 mbar to recover the 2-hydroxybenzonitrile, in the solid form.  
   
   
       24 . A process according to  claim 1 , characterized in that it consists of liquefying the gaseous reaction stream, then crystallizing the ammonium cyanophenate then carrying out solid/liquid separation to dissolve the solid product obtained in an organic solvent, preferably a polar solvent then heat treating the organic solution obtained.  
   
   
       25 . A process according to  claim 24 , characterized in that it consists of liquefying the gaseous reaction stream then crystallizing the ammonium cyanophenate then carrying out solid/liquid separation as described in one of  claims 21  to  23 .  
   
   
       26 . A process according to  claim 24 , characterized in that the solid product obtained is dissolved in an organic solvent, preferably a polar aprotic solvent, more preferably dimethylformamide or N-methylpyrrolidone.  
   
   
       27 . A process according to  claim 26 , characterized in that the organic ammonium cyanophenate solution undergoes a heat treatment at a temperature in the range 80° C. to 20° C., at a pressure in the range 1 mbar to 1 bar, preferably in the range 1 mbar to 500 mbar, to eliminate a light fraction (F 16 ) and to recover (F 17 ), which is 2-hydroxybenzonitrile in solution in a solvent (S 2 ).  
   
   
       28 . A process according to  claim 1 , characterized in that it consists of liquefying the gaseous reaction stream, treating it with an acid to obtain 2-hydroxybenzonitrile, and carrying out liquid/liquid separation to recover 2-hydroxybenzonitrile in the organic phase.  
   
   
       29 . A process according to  claim 28 , characterized in that the gaseous reaction stream (F 1 ) is liquefied by cooling from 90° C.-100° C. to a temperature of 40° C.-30° C. and bringing it into contact with water to eliminate the light compounds and to recover an aqueous phase comprising ammonium cyanophenate and ammonia.  
   
   
       30 . A process according to  claim 28 , characterized in that the ammonium ions are neutralized using a Brönsted acid with a pKa, measured in water, of less than 6, preferably in the range −1 to 4.  
   
   
       31 . A process according to  claim 30 , characterized in that the acid is sulphuric acid.  
   
   
       32 . A process according to  claim 30  or  claim 31 , characterized in that the quantity of acid employed is such that the pH obtained is in the range 6 to 1, preferably in the range 4 to 3.  
   
   
       33 . A process according to  claim 28 , characterized in that the reaction mixture obtained is decanted to separate an aqueous phase (F 19 ) comprising the excess acid and the ammonium salts and an organic phase (F 20 ) comprising 2-hydroxybenzonitrile.  
   
   
       34 . A process according to one of  claims 20  to  33 , characterized in that the 2-hydroxybenzonitrile is purified using the purification techniques defined in one of  claims 14  to  19 .  
   
   
       35 . A facility for separating 2-hydroxybenzonitrile from a gaseous reaction stream comprising 2-hydroxybenzonitrile, in the salt form, characterized in that it comprises: 
 a first column ( 1 ) intended to bring the gaseous reaction stream and the solvent (water and/or organic solvent) into contact;    a second column ( 2 ) the inlet to which is connected to the bottom of column ( 1 ), said column ( 2 ) being intended to produce a light fraction comprising ammonia, water and an alcohol (preferably methanol) from the column head and from the column bottom, a heavy fraction essentially comprising 2-hydroxybenzonitrile, the solvent (water and/or organic solvent), traces of ammonia and minor quantities of secondary products.    
   
   
       36 . A facility according to  claim 35 , characterized in that the first column ( 1 ) is a wash tower comprising means for admitting a gaseous reaction stream (F 1 ) to be treated and means for admitting a solvent (S 1 ), a vaporizing device (nozzles) and means for evacuating a heavy phase (liquid and/or gaseous) connected to a second column ( 2 ) which is supplied at mid-height, comprising cooling means (condenser) and provided in its upper portion with means for evacuating a gas phase comprising light compounds (F 2 ) and in its lower portion, means for withdrawing a liquid phase (F 3 ).  
   
   
       37 . A facility according to  claim 36 , characterized in that the separation unit is completed by a purification unit which is a distillation unit comprising a distillation column ( 3 ) supplied with the heavy fraction (F 3 ) deriving from the preceding column ( 2 ) and designed to obtain: 
 at the column head, different fractions at a pressure of 0.4 mbar: 
 light fractions with a boiling point of less than 40° C. at atmospheric pressure;  
 a fraction between 40° C. and 110° C. corresponding to phenol and to methyl salicylate;  
 a fraction at 110° C. corresponding to 2-hydroxybenzonitrile (F 4 );  
   and at the column bottom, different impurities (F 5 ) with a boiling point of more than 110° C.; salicylamide, N-methylsalicylamide and S-triazine.    
   
   
       38 . A facility according to  claim 37 , characterized in that the distillation column ( 3 ) has the following specifications: 
 number of theoretical stages: 5 to 40, preferably 10 to 30;    reflux ratio R in the range 1 to 10;    low residence time, preferably less than 30 minutes.    
   
   
       39 . A facility according to  claim 35 , characterized in that the separation unit is completed by a purification unit which is a crystallization unit comprising: 
 a crystallization reaction ( 4 ) provided with means for admitting the fraction (F 3 ) and a withdrawal device connected to the separation device ( 5 ) and provided with agitation means and a temperature regulating device;    a solid/liquid separation device ( 6 ), preferably an aspirator, agitated filter, filter-press, or multi-tube filter to recover a solid essentially constituted by 2-hydroxybenzonitrile and an aqueous phase (F 6 ) comprising the solvent, a little 2-hydroxybenzonitrile (less than 5% by weight) and by-products;    optionally, a drying means ( 6 ), preferably a rotary drier or an agitated drier, to recover 2-hydroxybenzonitrile in the form of a powder (P).    
   
   
       40 . A facility according to  claim 35 , characterized in that the separation unit is completed by a purification unit which is a refining unit comprising: 
 a cooling tower ( 7 ) provided with means for admitting the fraction (F 3 ) and a withdrawal device connected to a separation device ( 8 );    a liquid/liquid separation device ( 8 ), preferably a settler, to separate an aqueous phase (F 7 ) from an organic phase essentially constituted by 2-hydroxybenzonitrile (F 8 );    a reactor ( 9 ) provided with means for admitting an organic phase and provided with agitation means, a temperature regulating means (hot/cold), a distillation column and provided with a reduced pressurization system to separate, by distillation (F 9 ), the organic solvent and/or remaining water and to recover crude 2-hydroxybenzonitrile;    one or more refining devices, preferably of the draining sieve type to eliminate impurities (F 10 ) and to recover a liquid fraction of 2-hydroxybenzonitrile (F 11 ).    
   
   
       41 . A facility for separating 2-hydroxybenzonitrile by physical treatment of ammonium cyanophenate comprising: 
 a wash tower ( 11 ) provided with a system for admitting gas (F 1 ) and a device for introducing water via a pump that can recover a liquid phase (F 12 ) comprising water, crude ammonium cyanophenate and ammonia from the bottom; which mixture is transferred to reactor ( 12 );    a crystallization reactor ( 12 ) for the ammonium cyanophenate and provided with means for admitting the fraction (F 12 ) and a withdrawal device to connect it to a separation device ( 13 ); said reactor being provided with agitation means and a temperature regulating means;    a solid/liquid separation device ( 13 ), preferably an aspirator, agitated filter, filter-press, multi-tube filter to recover a solid essentially constituted by ammonium cyanophenate and an aqueous phase (F 13 ) comprising the solvent, a little 2-hydroxybenzonitrile (less than 5% by weight) and by-products;    drying means ( 14 ), preferably an agitated drier, in which it undergoes a temperature and pressure cycle to decompose the solid ammonium cyanophenate to 2-hydroxybenzonitrile, to recover 2-hydroxybenzonitrile in the form of a powder (P) while eliminating the solvent and remaining ammonia (F 14 ).    
   
   
       42 . A facility for separating 2-hydroxybenzonitrile by physical treatment of ammonium cyanophenate comprising: 
 a wash tower ( 11 ) provided with a system for admitting gas (F 1 ) and a device for introducing water via a pump that can recover a liquid phase (F 12 ) comprising water, crude ammonium cyanophenate and ammonia from the bottom; which mixture is transferred to a reactor ( 12 );    a crystallization reactor ( 12 ) for the ammonium cyanophenate and provided with means for admitting the fraction (F 12 ) and a withdrawal device to connect it to a separation device ( 13 ); said reactor being provided with agitation means and a temperature regulating means;    a solid/liquid separation device ( 13 ), preferably an aspirator, agitated filter, filter-press, multi-tube filter to recover a solid essentially constituted by ammonium cyanophenate and an aqueous phase (F 13 ) comprising the solvent, a little 2-hydroxybenzonitrile (less than 5% by weight) and by-products and provided with means for admitting a solvent (S 2 ) to dissolve the ammonium cyanophenate;    a reactor ( 16 ) provided with a device for admitting an organic solution of ammonium cyanophenate provided with agitation means, a temperature regulating device surmounted by a distillation column and provided with a reduced pressurization system to separate, by distillation, the organic solvent and/or remaining water (F 16 ) and to carry out thermal decomposition of ammonium cyanophenate to 2-hydroxybenzonitrile.    
   
   
       43 . A facility for separating 2-hydroxybenzonitrile by chemical treatment of a gaseous reaction stream comprising 2-hydroxybenzonitrile in the salt form, characterized in that it comprises: 
 a wash tower ( 17 ) provided with a system for admitting gas (F 1 ) and a device for introducing water via a pump that can recover a liquid phase (F 18 ) comprising water, crude ammonium cyanophenate and ammonia from the bottom; which mixture is transferred to a reactor ( 18 );    a neutralization reactor ( 18 ) provided with agitation means, a temperature regulating device, a device for introducing reactant (acid) and a pH regulating device (electrode): the lower portion of said reactor comprising a withdrawal device that can connect it to a device ( 19 );    a liquid/liquid separation device ( 13 ), preferably a settler for separating an aqueous phase (F 19 ) comprising excess acid and ammonium salts and an organic phase (F 20 ) comprising 2-hydroxybenzonitrile.    
   
   
       44 . A facility according to  claims 41  to  43 , characterized in that it is completed by a purification unit described in one of  claims 37  to  40 .  
   
   
       45 . A hydroxybenzonitrile type compound in the form of an ammonium salt with formula (III):  
     
       
         
         
             
             
         
       
     
     in which formula, R has the meanings given in  claim 2  or  claim 3 .  
   
   
       46 . Ammonium 2-cyanophenate with formula:  
     
       
         
         
             
             
         
       
       a liquid/liquid separation device ( 8 ), preferably a settler, to separate an aqueous phase (F 7 ) from an organic phase essentially constituted by 2-hydroxybenzonitrile (F 8 );  
       a reactor ( 9 ) provided with means for admitting an organic phase and provided with agitation means, a temperature regulating means (hot/cold), a distillation column and provided with a reduced pressurization system to separate, by distillation (F 9 ), the organic solvent and/or remaining water and to recover crude 2-hydroxybenzonitrile; and  
       one or more refining devices, preferably of the draining sieve type to eliminate impurities (F 10 ) and to recover a liquid fraction of 2-hydroxybenzonitrile (F 11 ).  
     
   
   
       88 . A facility for separating 2-hydroxybenzonitrile by physical treatment of ammonium cyanophenate comprising: 
 a wash tower ( 11 ) provided with a system for admitting gas (F 1 ) and a device for introducing water via a pump that can recover a liquid phase (F 12 ) comprising water, crude ammonium cyanophenate and ammonia from the bottom; which mixture is transferred to reactor ( 12 );    a crystallization reactor ( 12 ) for the ammonium cyanophenate and provided with means for admitting the fraction (F 12 ) and a withdrawal device to connect it to a separation device ( 13 ); said reactor being provided with agitation means and a temperature regulating means;    a solid/liquid separation device ( 13 ), agitated filter, filter-press, multi-tube filter to recover a solid essentially constituted by ammonium cyanophenate and an aqueous